Vestigated the mechanisms by which pyruvate improves cardiac function without the

Vestigated the mechanisms by which pyruvate improves cardiac function without the confounding variable of ischemia; however, there are very few investigations of the mechanisms of DCA in the absence of ischemia. Increased pyruvate levels purchase Pyrroloquinolinequinone disodium salt improve contractile performance during normoxia. Increased inotropy after administering exogenous pyruvate is due to increased TCA flux that increases mitochondrial NADH. Cytosolic phosphorylation potential is also elevated, as demonstrated in isolated perfused hearts, as well as in vivo. Higher / improves the efficiency of ATP-dependent processes such as sarco/endoplasmic reticulum Ca2+-ATPase and the actin-myosin ATPase. Abundant pyruvate also stabilizes the ryanodine receptor to reduce sarcoplasmic Ca2+ leak. The overall effect is greater SR Ca2+ load and release, increased force production, and increased availability of high-energy phosphates for contraction, all of which occur without a change in heart rate. The understanding of DCA mechanisms is incomplete without additional insight into how DCA might modulate function during normoxia. Indeed, administering DCA to cardiac tissue, whether normoxic or not, should shift substrate PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19850363 preference from endogenous fatty acids to carbohydrates. While fatty acids are the preferred substrate in normoxia, DCA administration causes fatty acid oxidation to drop to almost zero while glucose and pyruvate oxidation increase significantly, regardless of the presence of exogenous fat supply. Improved understanding of this effect of DCA in the normoxic perfused heart, and a comparison to the effect of administering exogenous pyruvate, could provide additional insight into the functional response of cardiac tissue to DCA. Pflugers Arch. Author manuscript; available in PMC 2016 January 06. Jaimes et al. Page 3 Our objective was to study the effects of DCA on PDH activation, downstream mitochondrial NADH production and consumption, calcium handling, myocardial contractile function, and the potential for causing arrhythmias in the normoxic perfused heart. Our approach was to compare the effects of activating PDH with either DCA or exogenous pyruvate. We hypothesized that administration of 5 mM pyruvate, with 6 mM glucose provided as fuel, would increase G5555 site steady-state NADH and LVDP. We hypothesized the administration of DCA, with 6 mM glucose provided as the fuel, would cause an initial increase in NADH concentration as PDH flux increased; however, this would be followed by a decrease in NADH due to an eventual PDH substrate limitation resulting from high PDH flux and increased demand for NADH secondary to increased LVDP. Furthermore, we predict DCA may increase the incidence of premature ventricular contractions due to reduced endogenous pyruvate concentration, which may blunt the stabilizing effects of pyruvate on RyR. We hypothesize that pyruvate depletion with DCA and downstream effects can be prevented with physiologic plasma concentrations of lactate and pyruvate . Two separate reservoirs and pumps provided constant circulation and heating of each perfusate solution and a valve at the aortic cannula allowed for immediate switching between perfusates. Pflugers Arch. Author manuscript; available in PMC 2016 January 06. Jaimes et al. Page 4 General protocol Author Manuscript Author Manuscript Author Manuscript Author Manuscript The initial perfusate was the KH solution described above. Hearts were closely monitored for electromechanical stability and signs of regional isch.Vestigated the mechanisms by which pyruvate improves cardiac function without the confounding variable of ischemia; however, there are very few investigations of the mechanisms of DCA in the absence of ischemia. Increased pyruvate levels improve contractile performance during normoxia. Increased inotropy after administering exogenous pyruvate is due to increased TCA flux that increases mitochondrial NADH. Cytosolic phosphorylation potential is also elevated, as demonstrated in isolated perfused hearts, as well as in vivo. Higher / improves the efficiency of ATP-dependent processes such as sarco/endoplasmic reticulum Ca2+-ATPase and the actin-myosin ATPase. Abundant pyruvate also stabilizes the ryanodine receptor to reduce sarcoplasmic Ca2+ leak. The overall effect is greater SR Ca2+ load and release, increased force production, and increased availability of high-energy phosphates for contraction, all of which occur without a change in heart rate. The understanding of DCA mechanisms is incomplete without additional insight into how DCA might modulate function during normoxia. Indeed, administering DCA to cardiac tissue, whether normoxic or not, should shift substrate PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19850363 preference from endogenous fatty acids to carbohydrates. While fatty acids are the preferred substrate in normoxia, DCA administration causes fatty acid oxidation to drop to almost zero while glucose and pyruvate oxidation increase significantly, regardless of the presence of exogenous fat supply. Improved understanding of this effect of DCA in the normoxic perfused heart, and a comparison to the effect of administering exogenous pyruvate, could provide additional insight into the functional response of cardiac tissue to DCA. Pflugers Arch. Author manuscript; available in PMC 2016 January 06. Jaimes et al. Page 3 Our objective was to study the effects of DCA on PDH activation, downstream mitochondrial NADH production and consumption, calcium handling, myocardial contractile function, and the potential for causing arrhythmias in the normoxic perfused heart. Our approach was to compare the effects of activating PDH with either DCA or exogenous pyruvate. We hypothesized that administration of 5 mM pyruvate, with 6 mM glucose provided as fuel, would increase steady-state NADH and LVDP. We hypothesized the administration of DCA, with 6 mM glucose provided as the fuel, would cause an initial increase in NADH concentration as PDH flux increased; however, this would be followed by a decrease in NADH due to an eventual PDH substrate limitation resulting from high PDH flux and increased demand for NADH secondary to increased LVDP. Furthermore, we predict DCA may increase the incidence of premature ventricular contractions due to reduced endogenous pyruvate concentration, which may blunt the stabilizing effects of pyruvate on RyR. We hypothesize that pyruvate depletion with DCA and downstream effects can be prevented with physiologic plasma concentrations of lactate and pyruvate . Two separate reservoirs and pumps provided constant circulation and heating of each perfusate solution and a valve at the aortic cannula allowed for immediate switching between perfusates. Pflugers Arch. Author manuscript; available in PMC 2016 January 06. Jaimes et al. Page 4 General protocol Author Manuscript Author Manuscript Author Manuscript Author Manuscript The initial perfusate was the KH solution described above. Hearts were closely monitored for electromechanical stability and signs of regional isch.